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annotate org.eclipse.swt.win32.win32.x86/src/org/eclipse/swt/internal/image/PngChunk.d @ 39:0ecb2b338560

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further work on phobosification
author Frank Benoit <benoit@tionex.de>
date Wed, 25 Mar 2009 13:20:43 +0100
parents f36c67707cb3
children 9f4c18c268b2
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1 /*******************************************************************************
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2 * Copyright (c) 2000, 2006 IBM Corporation and others.
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3 * All rights reserved. This program and the accompanying materials
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4 * are made available under the terms of the Eclipse Public License v1.0
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5 * which accompanies this distribution, and is available at
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6 * http://www.eclipse.org/legal/epl-v10.html
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7 *
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8 * Contributors:
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9 * IBM Corporation - initial API and implementation
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10 * Port to the D programming language:
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11 * Frank Benoit <benoit@tionex.de>
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12 *******************************************************************************/
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13 module org.eclipse.swt.internal.image.PngChunk;
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14
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15
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16 import org.eclipse.swt.SWT;
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17 import org.eclipse.swt.internal.image.LEDataInputStream;
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18 import org.eclipse.swt.internal.image.PngFileReadState;
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19 import org.eclipse.swt.internal.image.PngIhdrChunk;
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20 import org.eclipse.swt.internal.image.PngPlteChunk;
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21 import org.eclipse.swt.internal.image.PngIdatChunk;
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22 import org.eclipse.swt.internal.image.PngIendChunk;
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23 import org.eclipse.swt.internal.image.PngTrnsChunk;
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24 import java.lang.all;
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25
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26
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27 class PngChunk {
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28 byte[] reference;
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29
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30 static const int LENGTH_OFFSET = 0;
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31 static const int TYPE_OFFSET = 4;
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32 static const int DATA_OFFSET = 8;
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33
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34 static const int TYPE_FIELD_LENGTH = 4;
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35 static const int LENGTH_FIELD_LENGTH = 4;
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36 static const int MIN_LENGTH = 12;
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37
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38 static const int CHUNK_UNKNOWN = -1;
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39 // Critical chunks.
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40 static const int CHUNK_IHDR = 0;
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41 static const int CHUNK_PLTE = 1;
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42 static const int CHUNK_IDAT = 2;
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43 static const int CHUNK_IEND = 3;
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44 // Non-critical chunks.
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45 static const int CHUNK_tRNS = 5;
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46
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47 static /*const*/ byte[] TYPE_IHDR = cast(byte[])"IHDR";//{(byte) 'I', (byte) 'H', (byte) 'D', (byte) 'R'};
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48 static /*const*/ byte[] TYPE_PLTE = cast(byte[])"PLTE";//{(byte) 'P', (byte) 'L', (byte) 'T', (byte) 'E'};
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49 static /*const*/ byte[] TYPE_IDAT = cast(byte[])"IDAT";//{(byte) 'I', (byte) 'D', (byte) 'A', (byte) 'T'};
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50 static /*const*/ byte[] TYPE_IEND = cast(byte[])"IEND";//{(byte) 'I', (byte) 'E', (byte) 'N', (byte) 'D'};
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51 static /*const*/ byte[] TYPE_tRNS = cast(byte[])"tRNS";//{(byte) 't', (byte) 'R', (byte) 'N', (byte) 'S'};
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53 static int[] CRC_TABLE;
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54 //public static void static_this() {
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55 static this() {
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56 CRC_TABLE = new int[256];
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57 for (int i = 0; i < 256; i++) {
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58 CRC_TABLE[i] = i;
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59 for (int j = 0; j < 8; j++) {
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60 if ((CRC_TABLE[i] & 0x1) is 0) {
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61 CRC_TABLE[i] = (CRC_TABLE[i] >> 1) & 0x7FFFFFFF;
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62 } else {
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63 CRC_TABLE[i] = 0xEDB88320 ^ ((CRC_TABLE[i] >> 1) & 0x7FFFFFFF);
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64 }
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65 }
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66 }
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67 }
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68
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69 int length;
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70
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71 /**
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72 * Construct a PngChunk using the reference bytes
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73 * given.
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74 */
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75 this(byte[] reference) {
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76 setReference(reference);
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77 if (reference.length < LENGTH_OFFSET + LENGTH_FIELD_LENGTH) SWT.error(SWT.ERROR_INVALID_IMAGE);
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78 length = getInt32(LENGTH_OFFSET);
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79 }
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80
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81 /**
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82 * Construct a PngChunk with the specified number of
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83 * data bytes.
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84 */
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85 this(int dataLength) {
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86 this(new byte[MIN_LENGTH + dataLength]);
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87 setLength(dataLength);
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88 }
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89
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90 /**
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91 * Get the PngChunk's reference byteArray;
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92 */
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93 byte[] getReference() {
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94 return reference;
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95 }
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96
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97 /**
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98 * Set the PngChunk's reference byteArray;
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99 */
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100 void setReference(byte[] reference) {
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101 this.reference = reference;
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102 }
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103
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104 /**
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105 * Get the 16-bit integer from the reference byte
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106 * array at the given offset.
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107 */
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108 int getInt16(int offset) {
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109 int answer = 0;
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110 answer |= (reference[offset] & 0xFF) << 8;
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111 answer |= (reference[offset + 1] & 0xFF);
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112 return answer;
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113 }
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114
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115 /**
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116 * Set the 16-bit integer in the reference byte
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117 * array at the given offset.
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118 */
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119 void setInt16(int offset, int value) {
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120 reference[offset] = cast(byte) ((value >> 8) & 0xFF);
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121 reference[offset + 1] = cast(byte) (value & 0xFF);
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122 }
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123
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124 /**
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125 * Get the 32-bit integer from the reference byte
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126 * array at the given offset.
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127 */
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128 int getInt32(int offset) {
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129 int answer = 0;
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130 answer |= (reference[offset] & 0xFF) << 24;
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131 answer |= (reference[offset + 1] & 0xFF) << 16;
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132 answer |= (reference[offset + 2] & 0xFF) << 8;
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133 answer |= (reference[offset + 3] & 0xFF);
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134 return answer;
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135 }
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136
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137 /**
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138 * Set the 32-bit integer in the reference byte
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139 * array at the given offset.
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140 */
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141 void setInt32(int offset, int value) {
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142 reference[offset] = cast(byte) ((value >> 24) & 0xFF);
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143 reference[offset + 1] = cast(byte) ((value >> 16) & 0xFF);
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144 reference[offset + 2] = cast(byte) ((value >> 8) & 0xFF);
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145 reference[offset + 3] = cast(byte) (value & 0xFF);
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146 }
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147
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148 /**
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149 * Get the length of the data component of this chunk.
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150 * This is not the length of the entire chunk.
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151 */
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152 int getLength() {
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153 return length;
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154 }
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diff changeset
155
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
156 /**
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
157 * Set the length of the data component of this chunk.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
158 * This is not the length of the entire chunk.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
159 */
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
160 void setLength(int value) {
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
161 setInt32(LENGTH_OFFSET, value);
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
162 length = value;
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
163 }
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
164
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
165 /**
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
166 * Get the chunk type. This is a four byte value.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
167 * Each byte should be an ASCII character.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
168 * The first byte is upper case if the chunk is critical.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
169 * The second byte is upper case if the chunk is publicly defined.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
170 * The third byte must be upper case.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
171 * The fourth byte is upper case if the chunk is unsafe to copy.
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parents:
diff changeset
172 * Public chunk types are defined by the PNG Development Group.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
173 */
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
174 byte[] getTypeBytes() {
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
175 byte[] type = new byte[4];
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
176 System.arraycopy(reference, TYPE_OFFSET, type, 0, TYPE_FIELD_LENGTH);
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
177 return type;
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Frank Benoit <benoit@tionex.de>
parents:
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178 }
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
179
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
180 /**
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
181 * Set the chunk type. This is a four byte value.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
182 * Each byte should be an ASCII character.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
183 * The first byte is upper case if the chunk is critical.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
184 * The second byte is upper case if the chunk is publicly defined.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
185 * The third byte must be upper case.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
186 * The fourth byte is upper case if the chunk is unsafe to copy.
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187 * Public chunk types are defined by the PNG Development Group.
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188 */
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
189 void setType(byte[] value) {
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
190 if (value.length !is TYPE_FIELD_LENGTH) {
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
191 SWT.error (SWT.ERROR_INVALID_ARGUMENT);
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Frank Benoit <benoit@tionex.de>
parents:
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192 }
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
193 System.arraycopy(value, 0, reference, TYPE_OFFSET, TYPE_FIELD_LENGTH);
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Frank Benoit <benoit@tionex.de>
parents:
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194 }
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195
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
196 /**
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
197 * Get the chunk's data.
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parents:
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198 */
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parents:
diff changeset
199 byte[] getData() {
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
200 int dataLength = getLength();
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
201 if (reference.length < MIN_LENGTH + dataLength) {
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
202 SWT.error (SWT.ERROR_INVALID_RANGE);
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Frank Benoit <benoit@tionex.de>
parents:
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203 }
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
204 byte[] data = new byte[dataLength];
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
205 System.arraycopy(reference, DATA_OFFSET, data, 0, dataLength);
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
206 return data;
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
207 }
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
208
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
209 /**
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
210 * Set the chunk's data.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
211 * This method has two side-effects.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
212 * 1. It will set the length field to be the length
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
213 * of the data array given.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
214 * 2. It will set the CRC field to the computed CRC
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
215 * value of the data array given.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
216 */
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
217 void setData(byte[] data) {
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
218 setLength(data.length);
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
219 System.arraycopy(data, 0, reference, DATA_OFFSET, data.length);
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
220 setCRC(computeCRC());
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
221 }
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
222
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
223 /**
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
224 * Get the CRC value for the chunk's data.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
225 * Ensure that the length field has a good
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
226 * value before making this call.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
227 */
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
228 int getCRC() {
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
229 int crcOffset = DATA_OFFSET + getLength();
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
230 return getInt32(crcOffset);
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
231 }
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
232
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
233 /**
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
234 * Set the CRC value for the chunk's data.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
235 * Ensure that the length field has a good
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
236 * value before making this call.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
237 */
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
238 void setCRC(int value) {
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
239 int crcOffset = DATA_OFFSET + getLength();
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
240 setInt32(crcOffset, value);
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
241 }
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
242
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
243 /**
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
244 * Get the chunk's total size including the length, type, and crc fields.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
245 */
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
246 int getSize() {
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
247 return MIN_LENGTH + getLength();
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
248 }
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
249
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
250 /**
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
251 * Compute the CRC value for the chunk's data. Answer
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
252 * whether this value matches the value stored in the
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
253 * chunk.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
254 */
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
255 bool checkCRC() {
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
256 int crc = computeCRC();
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
257 int storedCRC = getCRC();
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
258 return crc is storedCRC;
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
259 }
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
260
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
261 /**
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
262 * Answer the CRC value of chunk's data.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
263 */
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
264 int computeCRC() {
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
265 int crc = 0xFFFFFFFF;
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
266 int start = TYPE_OFFSET;
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
267 int stop = DATA_OFFSET + getLength();
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
268 for (int i = start; i < stop; i++) {
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
269 int index = (crc ^ reference[i]) & 0xFF;
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
270 crc = CRC_TABLE[index] ^ ((crc >> 8) & 0x00FFFFFF);
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
271 }
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
272 return ~crc;
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
273 }
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
274
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
275 bool typeMatchesArray(byte[] array) {
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
276 for (int i = 0; i < TYPE_FIELD_LENGTH; i++) {
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
277 if (reference[TYPE_OFFSET + i] !is array[i]){
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
278 return false;
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
279 }
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
280 }
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
281 return true;
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
282 }
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
283
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
284 bool isCritical() {
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
285 char c = cast(char) getTypeBytes()[0];
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
286 return 'A' <= c && c <= 'Z';
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
287 }
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
288
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
289 int getChunkType() {
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
290 if (typeMatchesArray(TYPE_IHDR)) return CHUNK_IHDR;
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
291 if (typeMatchesArray(TYPE_PLTE)) return CHUNK_PLTE;
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
292 if (typeMatchesArray(TYPE_IDAT)) return CHUNK_IDAT;
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
293 if (typeMatchesArray(TYPE_IEND)) return CHUNK_IEND;
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
294 if (typeMatchesArray(TYPE_tRNS)) return CHUNK_tRNS;
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
295 return CHUNK_UNKNOWN;
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
296 }
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
297
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
298 /**
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
299 * Read the next PNG chunk from the input stream given.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
300 * If unable to read a chunk, return null.
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
301 */
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
302 static PngChunk readNextFromStream(LEDataInputStream stream) {
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
303 try {
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
304 int headerLength = LENGTH_FIELD_LENGTH + TYPE_FIELD_LENGTH;
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
305 byte[] headerBytes = new byte[headerLength];
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
306 int result = stream.read(headerBytes, 0, headerLength);
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
307 stream.unread(headerBytes);
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
308 if (result !is headerLength) return null;
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
309
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
310 PngChunk tempChunk = new PngChunk(headerBytes);
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
311
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
312 int chunkLength = tempChunk.getSize();
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
313 byte[] chunk = new byte[chunkLength];
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Frank Benoit <benoit@tionex.de>
parents:
diff changeset
314
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
315 result = stream.read(chunk, 0, chunkLength);
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
diff changeset
316 if (result !is chunkLength) return null;
6dd524f61e62 add dwt win and basic java stuff
Frank Benoit <benoit@tionex.de>
parents:
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317
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318 switch (tempChunk.getChunkType()) {
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319 case CHUNK_IHDR:
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320 return new PngIhdrChunk(chunk);
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321 case CHUNK_PLTE:
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322 return new PngPlteChunk(chunk);
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323 case CHUNK_IDAT:
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324 return new PngIdatChunk(chunk);
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325 case CHUNK_IEND:
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326 return new PngIendChunk(chunk);
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327 case CHUNK_tRNS:
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328 return new PngTrnsChunk(chunk);
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329 default:
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330 return new PngChunk(chunk);
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331 }
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332 } catch (IOException e) {
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333 return null;
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334 }
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335 }
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336
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337 /**
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338 * Answer whether the chunk is a valid PNG chunk.
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339 */
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340 void validate(PngFileReadState readState, PngIhdrChunk headerChunk) {
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341 if (reference.length < MIN_LENGTH) SWT.error(SWT.ERROR_INVALID_IMAGE);
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342
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343 byte[] type = getTypeBytes();
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344
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345 // The third character MUST be upper case.
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346 char c = cast(char) type[2];
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347 if (!('A' <= c && c <= 'Z')) SWT.error(SWT.ERROR_INVALID_IMAGE);
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348
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349 // All characters must be letters.
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350 for (int i = 0; i < TYPE_FIELD_LENGTH; i++) {
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351 c = cast(char) type[i];
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352 if (!(('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z'))) {
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353 SWT.error(SWT.ERROR_INVALID_IMAGE);
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354 }
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355 }
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356
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357 // The stored CRC must match the data's computed CRC.
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358 if (!checkCRC()) SWT.error(SWT.ERROR_INVALID_IMAGE);
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359 }
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360
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361 /**
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362 * Provided so that subclasses can override and add
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363 * data to the toString() call.
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364 */
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365 String contributeToString() {
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366 return "";
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367 }
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368
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369 /**
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370 * Returns a string containing a concise, human-readable
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371 * description of the receiver.
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372 *
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373 * @return a string representation of the event
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374 */
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375 public override String toString() {
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376 String buffer = Format( "{\n\tLength: {}\n\tType: {}{}\n\tCRC: {:X}\n}",
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377 getLength(),
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378 cast(String) getTypeBytes(),
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379 contributeToString(),
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380 getCRC());
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381 return buffer;
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382 }
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383
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384 }